shotwell: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/shotwell - from package: shotwell

You may install the required package with command apt-get install {package}

Error in other languages:
shotwell: bevel nie gevind nie
shotwell: comandă negăsită
shotwell: comando não encontrado
shotwell: commande introuvable
shotwell: command not found
shotwell: käsku ei ole
shotwell: không tìm thấy lệnh
shotwell: komanda nerasta
shotwell: Kommando nicht gefunden.
shotwell: kommandot finns inte
shotwell: komut yok
shotwell: nie znaleziono polecenia
shotwell: níor aimsíodh an t-ordú
shotwell: no se encontró la orden
shotwell: no s'ha trobat l'ordre
shotwell: opdracht niet gevonden
shotwell: parancs nem található
shotwell: perintah tidak ditemukan
shotwell: príkaz nenájdený
shotwell: příkaz nenalezen
shotwell: команда не найдена
shotwell: командата не е открита
shotwell: 命令找不到
shotwell: コマンドが見つかりません